1) Field of the Invention
The present invention relates to medical devices and, in particular, to a medical device for treating a target site within the body, such as a vascular abnormality, proximate to a bifurcated lumen.
2) Description of Related Art
An aortic aneurysm is a weak area in the aorta, the main blood vessel that carries blood from the heart to the rest of the body. A common aneurysm is the abdominal aortic aneurysm (“AAA”), which may be caused by arteriosclerosis. As blood flows through the aorta, the weak vessel wall thins over time and expands like a balloon and can eventually burst if the vessel wall gets too thin. Most commonly, aortic aneurysms occur in the portion of the vessel below the renal artery origins. The aneurysm may be located in the vessels supplying the hips and pelvis, including the iliac arteries.
Rather than performing surgery to repair an aneurysm, vascular surgeons may install an endovascular stent graft delivered to the site of the aneurysm using elongated catheters. A stent graft can be used for a variety of conditions involving the blood vessels, but most commonly is used to reinforce an aneurysm. The stent graft may be delivered to a location bridging the aneurysm, at which point the stent graft is deployed and expanded to approximately the normal diameter of the aorta at that location. Over time, the stent graft becomes endothelialized and the space between the outer wall of the stent graft and the aneurysm ultimately fills with clotted blood, which prevents the aneurysm from growing further since the stent graft bypasses (excludes) the aneurysm and prohibits systematic pressure and flow on the weakened segment of the lumen.
Depending on where the aneurysm is in relation to other branch vessels, different design variations may be needed. For example, in treating an AAA, the stent graft should be placed so as not to exclude blood flow through the renal arteries which branch off from the abdominal aorta. Moreover, the stent graft should be anchored within the lumen to reduce the incidence of migration, such as by promoting endothelialization or fixation with the lumen. Endoleaks may occur as a result of blood flowing around the stent, which may result in further weakening of the site of the aneurysm.
In order to treat an AAA, bifurcated stent grafts have been employed. In particular, the bifurcated stent graft typically includes a main portion configured to bridge the aneurysm below the renal arteries and a pair of tubular portions extending from the main portion that are configured to extend into respective iliac arteries. The bifurcated stent graft is most commonly delivered through one of the iliac arteries. Thus, the delivery of the bifurcated stent graft may be complicated when attempting to position the tubular portions of the bifurcated stent graft into respective iliac arteries while also ensuring that the main portion is secured within the aorta upstream of the aneurysm without blocking the renal arteries.
Furthermore, the size of the delivery catheter may affect the ability of the surgeon to manipulate the catheter within the lumen, often reduced in size due to arteriosclerosis, and may result in trauma to the vascular tissue. Thus, the smaller the delivery catheter, the less trauma to the tissue should occur, and the medical device should be more easily and accurately positioned within the lumen. Smaller delivery catheters would also allow a physician access to smaller vessels, so as to more proactively treat aneurysms. Also, smaller aneurysms are typically easier to treat than larger aneurysms (e.g., aneurysms of at least 5 cm in diameter) because smaller aneurysms are more centrally located between the renal arteries and the iliac bifurcation and also because small aneurysms are more symmetrical and usually do not yet include tortuosity nor involve the iliac arteries.
The profile for delivery of a bifurcated stent graft is determined by the size of the main portion and each tubular portion of the bifurcated stent graft, as well as the configuration of the tubular portions in the delivery catheter such as branch portions placed side by side. It would be advantageous, if all the benefits of a bifurcated stent graft could be achieved with a lower delivery profile. A lower delivery profile would provide for a smaller sized delivery catheter, a smaller puncture size into the vasculature, and less trauma to the vascular tissue in passage of the delivery catheter through the vasculature. In addition, smaller catheters are more flexible, and the device may be able to be placed in more difficult to reach anatomical sites such as through smaller diameter vessels or through more tortuous pathways.
Therefore, there is a need for a medical device that is capable of effectively treating various target sites within the body such as an AAA. Moreover, there is a need for a medical device that may be easily delivered and adequately anchored at a target site such as within the aorta and common iliac arteries. In addition, there is a need for a medical device that may be delivered to a target site that is less traumatic to the vasculature and that may be used to prophylactically treat various conditions that may be more difficult to reach in the anatomy.